1. Field of the Invention
The present invention relates to a method of manufacturing an ink jet recording head for generating droplets of a recording liquid for use in the ink jet recording process.
2. Description of the Prior Art
An ink jet recording head used in the ink jet recording process generally comprises outlets for ejecting tiny drops of a recording liquid (hereinafter called orifices), a liquid flow path, and liquid ejection energy generating portions provided in a part of the liquid flow path. To obtain high grade images by such an ink jet recording head, it is desirable that droplets of recording liquid be ejected from the respective orifices always in the same volumes at the same speeds. To fulfill this condition, Japanese Patent Application Laid-open Nos. 10940/1992 to 10942/1992 disclose methods comprising applying driving signals to ink ejection pressure generating elements (electro-thermal conversion elements) in response to recorded information to cause the electro-thermal conversion elements to generate heat energy inducing a rapid temperature increase surpassing the nucleate boiling of the ink, thereby forming bubble in the ink, and ejecting ink droplets through the communication of the bubble with the atmosphere.
The ink jet recording head for accomplishing the above methods preferably provides a shorter distance between the electro-thermal conversion element and the orifice (hereinafter called the OH distance). In the above method, it is necessary that the OH distance can be set accurately and with good reproducibility, since this parameter virtually determines the ejection volume.
Conventional methods of manufacturing ink jet recording heads include a method as described in Japanese Patent Application Laid-open Nos. 208255/1982 to 208256/1982 which comprises pattern-forming a nozzle comprising ink flow paths and orifice portions on a substrate with the use of a photosensitive resin material, the substrate having ink ejection pressure generating elements thereon, and then joining a cover such as a glass sheet onto the nozzle. Also included is a method as described in Japanese Patent Application Laid-open No. 154947/1986 which comprises forming an ink flow path pattern using a dissoluble resin, coating the pattern with an epoxy resin or the like, followed by curing the resin, cutting the base plate, and then removing the dissoluble resin pattern by dissolving. All these methods produce ink jet recording heads of the type in which the direction of growth of bubble and the direction of ejection of ink droplets are different (nearly perpendicular). With such a type of recording head, the distance between the ink ejection pressure generating element and the orifice is set by cutting the base plate, so that the accuracy and precision of cutting are a very important factor in controlling the distance between the ink ejection pressure generating element and the orifice. However, cutting is generally performed by a mechanical means such as a dicing saw, thus making it difficult to realize high precision and accuracy.
A method of manufacturing an ink jet recording head of the type in which the directions of bubble growth and ink droplet ejection are almost identical is described in Japanese Patent Application Laid-open No. 8658/1983 which Comprises joining together a substrate and a dry film serving as an orifice plate via another patterned dry film, and then forming orifices by photolithography. Another such method described in Japanese Patent Application Laid-open No. 264975/1987 comprises joining together a substrate having ink ejection pressure generating elements formed thereon and an orifice plate produced by electroforming via a patterned dry film. Both these methods pose difficulty in preparing thin (e.g. 20 .mu.m or less), uniform orifice plates. Even if such a thin and uniform orifice plate was prepared, the step of joining it to the substrate having ink ejection pressure generating elements formed thereon is very difficult to perform because the orifice plate is fragile.